Internal combustion engines have a crankshaft and a camshaft coupled with the crankshaft. One cycle of a four-stroke internal combustion engine comprises the aspiration, compression, expansion and expulsion strokes. One cycle of a four-stroke internal combustion engine requires 720 degrees of crankshaft angle and therefore a first and a second rotation of the crankshaft. To sense the crankshaft angle, incremental position sensors are very frequently used which for example comprise a pickup wheel configured as a toothed wheel with a specified number of teeth and a sensor element whose measurement signal is for example representative of the respective teeth. Such sensor elements are for example sensors which function according to the Hall principle.
To establish a reference position of the crankshaft, the pickup wheel typically exhibits an enlarged gap between two teeth. Solely on the basis of the measurement signal from the crankshaft angle sensor it is not possible to draw a conclusion as to which rotation the crankshaft is performing within the respective cycle, but this information is essential for operating the internal combustion engine.
To determine which of the two crankshaft angle rotations the internal combustion engine is performing within a cycle, a camshaft angle sensor can for example be used.
In addition, it is known that adjustment devices can be provided in a specified position of the crankshaft for adjusting a phase between a reference mark on the crankshaft and a reference mark on the camshaft. For example, from DE 101 08 055 C1 a method is known for determining the phase position of a camshaft in relation to a crankshaft in which the phase position is determined according to the camshaft angle sensed and the crankshaft angle sensed.
From DE 199 34 112 A1 it is known that a pressure in a fuel rail can be sensed by means of a pressure sensor. It is also known from DE 199 34 112 A1 that if the phase position of ignition and injection is wrong by 360 degrees of crankshaft when starting, fuel will be blown back into an affected injection valve by compression counterpressure. This leads to an increase in pressure in the fuel rail, which is sensed by the pressure sensor. An analog/digital comparator switch is provided, by means of which such a signal can be assessed. Depending on the signal thus assessed, ignition and injection are re-synchronized by 360 degrees of crankshaft.
From DE 101 15 262 A1 it is known that when a single-cylinder fuel pump of an internal combustion engine is used, a characteristic increase in pressure is to be observed once per rotation of the camshaft. Given the rigid coupling between the fuel pump and the camshaft, the camshaft position can be determined on the basis of the point in time at which the increase in pressure starts.